1. Field of the Invention
The present invention relates to a cylindrical lever lock capable of preventing a lever from drooping or malfunctioning due to deformation of related parts although being repetitively used or applied with a strong wrenching force during opening and closing of a door, and also capable of reducing the manufacturing cost.
2. Description of the Related Art
A door lock is generally used in various public facilities including public or commercial buildings such as schools, government and public offices, hospitals, and hotels, and such a door lock mostly employs a cylindrical lever lock using a thin and long lever as a handle so that even the disabled and the old are able to conveniently use the lever lock. The lever additionally employs a spring to return the lever rotated to open or close the door to its initial position.
Generally, the lever of the cylindrical lever lock is mounted in a horizontal position for convenient use and applied with a strong wrenching force due to leverage when rotated to open and close a door. Here, the strong wrenching force is totally transmitted to component parts of the lever lock, thereby damaging or deforming related parts. Furthermore, in this case, the related parts may be spaced and the lever may be drooped. As a result, not only the appearance but also the function as a locking device may be deteriorated.
Accordingly, the cylindrical lever lock needs to be manufactured to technically overcome all the above problems. Furthermore, an interval adjusting device is also required for compatible use of the cylindrical lever lock in any type of doors.
KR Utility Model No. 170492 suggests a cylinder-type door lock most satisfactorily meeting the above necessities. The cylinder-type door lock is structured in a manner that springs for preventing drooping of levers are elastically connected to inner and outer attachment plates each including a mounting recess and a fixing protrusion through movable plates. In addition, a supporting plate is fixedly connected through a fixing hole and the fixing protrusion, thereby achieving the drooping prevention function. Also, a locking nut formed at the outside and inner and outer interval maintaining plates are provided so that the interval of parts can be adjusted according to thickness of a door.
However, the inner and outer attachment plates of the conventional art are almost impossible to manufacture using general metal plates because those are thick and structurally complicated since having the mounting recess, the fixing protrusion and the fixing hole. Therefore, casting of Zn or Al is required, which will increase the material cost and the process cost, consequently increasing the manufacturing cost.
Also, the inner and outer attachment plates and the movable plate which are essential parts requiring great strength are not sufficiently durable against the wrenching force since being made of non-ferrous metal having low strength. Nevertheless, the supporting plate to prevent separation of the springs is connected with the fixing holes and the fixing protrusions of the inner and outer attachment plates. Therefore, in case that an excessive force is applied in the wrenching direction while the door is being opened or closed by rotation of the lever, the fixing protrusions of the plates may be deformed and accordingly the supporting plate, the movable plates and the springs may be separated from the inner and outer attachment plates. As a result, the lever lock cannot normally operate, thus finishing the lifespan.
Especially, the lever is structured such that a rotation angle thereof is restricted by a stopper protrusion formed at an end of a guiding tube of each of the inner and outer attachment plates. Therefore, if an excessive force is applied through the lever, the guiding tube of the plates made of Zn or Al would be easily deformed. Also, since the movable plate is in the form of a flat panel very susceptible to wrench, a rim of the movable plate may be deformed and spaced, accordingly causing drooping of the lever. Moreover, friction around the deformed part will hinder a favorable operation of the lever.
Furthermore, since the locking nut is prepared in addition to the interval maintaining plates in order to adjust interval among the component parts according to thickness of the door, the processes will take much time and become complicated during pre-assembling for shipment of the product or during disassembling and installation in the field.